The invention relates to a pin-type holding element for an orthopaedic holding system with an elastically compressible, head-shaped widened portion and with a central opening, into which a core may be inserted, which prevents an elastic compression of the head-shaped widened portion by filling out the central opening in the region of the widened portion without expanding this.
Such a pin-type holding element is proposed in the German patent application 195 45 612.2-35. It is used, for example, for fixing bone plates to bones, the holding elements in this case being constructed as bone screws. These bone screws are inserted into openings in the bone plate, the edge of which is undercut, i.e. the diameter of the edge is larger in the centre than on the top and bottom of the bone plate As a result, the head-shaped widened portion, which is constructed in the form of a spherical ring in the known case, is held in the opening of the bone plate so as to be undetachable in axial direction, but be able to rotate and swivel freely.
A holding pin is described in WO95/35067, the cylindrical widened portion of which is held in a similar manner in a spherical ring, which is in turn mounted in an opening of a bone plate so as to be able to rotate and swivel freely.
If such a holding pin, which may be inserted into a bone plate or into a bearing ring through elastic compression, is to be secured axially in this position, it has been proposed in the German patent application to prevent the elastic compression of the head-shaped widened portion through a core, which is inserted into a central opening of the pin-type holding element and fills out this central opening in the region of the widened portion in such a way that the parts of the head-shaped widened portion can no longer be moved elastically radially inwards
If such a connection is to be released again, it is necessary to remove the core from the central opening. This is obstructive in an operation, since the holding element is then divided into two parts, one part of which has to be removed from the operating area.